The interdental plate refers to the bone-filled mesial-distal region between the teeth. [ http://en.wikipedia.org/wiki/Interdental_plate ]
Term information
In paleobiology, the presence or absence of the interdental plate can determine the place of an animal in the evolutionary scale, and paleontologists use the interdental plate when trying to classify a new specimen. Thecodont reptiles and theropod dinosaur fossils have an interdental plate, whereas acrodont reptiles such as Sphenodontia do not.[3] Its presence in Archaeopteryx, an extinct avian, resulted in the proposal of the dinosaur-bird connection